Field of the Invention
This invention relates to a process for producing a fish meal and a fish oil. More particularly, it relates to a process for producing a fish meal and a fish oil that scarcely undergoing thermal denaturation, which comprises treating fish bodies with a protease at a relatively low temperature and dividing and drying the treated matters each at a relatively low temperature.
This invention further relates to a process for producing a protein-rich fish meal suitable as a protein source for, e.g., feeds, baits and pet foods. More particularly, it relates to a process for producing a fish meal which contains a small amount of ash as well as a large amount of partially decomposed and scarcely denatured crude protein.
Fish meal and fish oil have been produced from fish bodies and processing residue thereof by optionally pretreating, for example, cutting, crushing or grinding the raw material; boiling the treated material; pressing the same to thereby separate liquid matters containing a fish oil; drying the residual solid matters optionally together with fish-solubles, which will be described hereinafter; grinding the material, if required, to thereby give a fish meal; while separating the fish oil from the liquid matters; and concentrating the residual liquid matters to thereby give fish-solubles.
Since the abovementioned process involves high temperature heating processe(es) such as boiling, proteins contained in the fish meal thus obtained are thermally denatured ones, which makes the product not always satisfactory as a proteinaceous feed in some cases.
In addition, the fish oil produced by the above process is also a thermally denatured one. Thus it is difficult to obtain a fish oil of excellent qualities thereby.
An example of known methods for producing a crude protein-rich fish meal comprises employing white-meat fish rich in crude protein as the starting material. However this method cannot be widely employed since the material sources are limited and the materials are generally expensive. In order to overcome these problems, Japanese Patent Laid-Open No. 156370/1985 has proposed a process wherein a conventional fish meal is divided into a portion rich in fish bones (i.e., ash) and another portion containing a small amount of the same. However the fish bone-rich portion as obtained by the above process still contains a significantly large amount of protein. Thus this process is unsatisfactory from the viewpoint of the effective utilization of protein.
A conventional process for producing a fish meal involves high-temperature heating step(s) such as boiling. Thus the obtained fish meal is a thermally denatured one, which sometimes makes it unsatisfactory as a protein source for feeds, baits or pet foods.